The present invention relates to a liquid crystal projector equipment that can be built compact by reducing the number of parts by using narrow-band polarizing beam splitters or narrow-band phase plates or the like.
A conventional liquid crystal projector equipment using a reflex liquid crystal plate as is shown in FIG. 1, for example, comprises lens arrays 2 and 4 and lens 5 for collecting white light from light source 1, dichroic mirrors 71 and 72 for separating the white light into lights of three different colors, namely, the light of red color range, light of green color range and light of blue color range, polarizing beam splitter (PBS) 74R, 74G and 74B for separating s-polarized-light components of the lights of respective color ranges to let the separated s-polarized-light components of the light fall on reflex liquid crystal plates 10R for red color range 10G for green color range and 10B for blue color range respectively, cross dichroic prism 75 for synthesizing the image lights of p-polarized-light components of the color ranges which are modulated and reflected to be output, and projection lens 12 for projecting the image light on a screen.
Such a conventional liquid crystal projector equipment is required to comprise not only a relatively expensive cross dichroic prism 75 but also the reflex liquid crystal plates 10R, 10G and 10B arranged so as not interfere one another in each of optical paths of the light separated into the lights of red color range, green color range and blue color range, which results in the increase in the size of casing.
An object of the present invention, reflecting such problem, is to reduce the size of the equipment by reducing the number of the dichroic mirrors through the use of filters and by providing color separation function through the use of the PBS having narrow-band characteristic or by using xc2xd phase plate having narrow-band characteristic.
The liquid crystal projector equipment according to the present invention comprises a light source for outputting a white light, a first dichroic mirror for reflecting the green-color-range light from the light source while transmitting the red-color-range light and blue-color-range light therefrom, a first PBS for reflecting s-polarized-light component, a reflex liquid crystal plate for green color range for receiving, modulating, reflecting and outputting, through the first PBS, the green-color-range light from the first PBS, a second PBS for reflecting s-polarized-light components of the red-color-range light and blue-color-range light while transmitting the p-polarized-light component thereof, a reflex liquid crystal plate for blue color range designed for receiving s-polarized-light component from the second PBS through a blue-color-range light transmitting filter and modulating and reflecting the s-polarized-light component for output through the second PBS, a reflex liquid crystal plate for red color range designed for receiving p-polarized-light component from the second PBS through the blue-color-range light transmitting filter and modulating and reflecting the p-polarized-light component for output by being reflected by the second PBS, a first dichroic prism for transmitting the image light of green color range from the first PBS while reflecting the image light of blue color range and the image light of red color range from the second PBS, and a projection lens for projecting the image light from the first dichroic prism on a screen.
Further, the equipment may comprise a third PBS for separating the s-polarized-light component of the green-color-range light from the light source so that the light from the third PBS is made to fall on the reflex liquid crystal plate for the green color range and to be modulated and reflected for being output by passing through the third PBS.
Alternatively, the equipment may comprise a fourth PBS and a first xc2xd phase plate for transmitting the s-polarized-light component of the blue-color-range light and rotating 90xc2x0 its plane of polarization to convert the s-polarized-light component into p-polarized-light component placed in the preceding stage of the second PBS so that the s-polarized-light component (blue-color-range light) reflected by the second PBS falls directly on the reflex liquid crystal plate for blue color range, while the p-polarized-light component (red-color-range light) that has passed through the second PBS falls directly on the reflex liquid crystal plate for red color range, thereby enabling to do without the filters for blue-color-range light and red-color-range light.
Further alternatively, the equipment may comprise the fourth PBS for adjusting the light from said light source to the s-polarized-light component of the light so that the light from the fourth PBS falls on the first dichroic mirror; the light from the first dichroic mirror falls on the second PBS by way of the first xc2xd phase plate; the s-polarized-light component (blue-color-range light) is reflected by the second PBS while transmitting the p-polarized-light component (red-color-range light); the s-polarized-light component from the second PBS falls on the reflex liquid crystal plate for blue color range, and the s-polarized-light component is modulated and reflected to be output by passing through the second PBS; the p-polarized-light component from the second PBS falls on the reflex liquid crystal plate for red-color-light range, and the p-polarized-light component is modulated and reflected by the second PBS for output.
Further alternatively, the equipment may comprise a second dichroic mirror designed for transmitting green-color-range light from the fourth PBS while reflecting red-color-range light and blue-color-range light so that the green-color-range light from the second dichroic mirror falls on the reflex liquid crystal plate for green color range by way of the fist PBS and the blue-color-range light and red-color-range light fall on the 1-xc2xd phase plate.
Further, the equipment may comprise a second xc2xd wavelength plate for rotating 90xc2x0 the plane of polarization of the light of total wavelength range provided before a reflex liquid crystal plate for red color range so that the p-polarized-light component from the second PBS can be converted into the s-polarized-light component and the s-polarized-light component incident method similar to those for blue color range and green color range can be applied to the reflex liquid crystal plate for red color range.
Further, the equipment may comprise a fifth PBS capable of outputting only the p-polarized-light component of the light from the light source, a second xc2xd wavelength plate so that for rotating 90xc2x0 the plane of polarization of the p-polarized-light component of red color range from the fifth PBS while transmitting the p-polarized-light components of the blue-color-range light and green-color-range light, a sixth PBS for reflecting the s-polarized-light component (red-color-range light) from the first xc2xd phase plate while transmitting the p-polarized-light component (blue-color-range light and green-color-range light), a second dichroic prism for transmitting the p-polarized-light component of blue-color-range light from the sixth PBS, while reflecting the green-color-range light, making the s-polarized-light component from the sixth PBS fall on a reflex liquid crystal plate for red color range, making the blue-color-range light from the second dichroic prism fall on the reflex liquid crystal plate for blue color range, making the green-color-range light fall on the reflex liquid crystal plate for green color range, and making the image light modulated and reflected by each of the reflex liquid crystal plates for various color ranges to be projected on a screen by a projection lens by way of the sixth PBS.
In this case, when the second xc2xd wavelength plate is provided before the reflex liquid crystal plate for converting the s-polarized-light component from the sixth PBS into the p-polarized-light component, the p-polarized-light incidence type reflex liquid crystal plate similar to those for blue color range and green color range can be used.